1. Field of the Invention
The invention of the present application relates generally to the field of extruded sign frame sections. More particularly, this invention relates to a device which may be used as a frame for flexible faced signs, canopies and related applications, where the display surface is made of a flexible cloth material.
2. Description of Related Technology
The modern sign industry has been revolutionized by the development of soft, cloth-like, stretchable fabric materials for use as a display face. One such material is marketed by the 3M Company under the trademark "PANAFLEX", and has a weight comparable to that of heavy canvas. It presents a smooth surface and is translucent, allowing for internal illumination. This material is a polyvinyl chloride which is reinforced with glass fibers that are woven into the material in a pattern resembling that of a rectangular grid. As a consequence of the manner of fabrication, it is virtually impossible to tear the material. Even if the material is cut, the cut is difficult to extend by further tearing. If the material is cut, the perforation can easily be patched in the field in a manner similar to and no more difficult than applying a patch to an innertube. The material is capable of withstanding substantial wind loads.
When used as a sign face material, the fabric must be mounted in some sort of framework. One sign may weigh several thousand pounds. Frequently, such a sign will have a display face area of hundreds of square feet. The framework must be extremely rugged to support the weight of a larger sign and to withstand high winds.
In order to achieve the ruggedness necessary for larger signs, such signs have long been fabricated as steel frameworks. Improvements in sign framework construction have been made during recent years through the use of aluminum extrusions to form the cabinet and to serve as a base for mounting the components used to support the display face. The use of aluminium results in a substantial decrease in weight and a reduction in the rate of frame corrosion.
Extruded aluminum shapes are now quite commonly employed in the construction of sign frames. Literally thousands of extruded aluminum shapes are available to the sign industry, the large number of shapes available serving as evidence of a continuing search in the industry for improvement and a lack of satisfaction with presently available designs. The fundamental problem relates to the difficulty in easily and securely fastening the flexible sign face material to the frame extrusion.
The conventional manner of mounting flexible translucent sign faces, such as "PANAFLEX," requires a relatively complicated clamping arrangement for securing the perimeter of the sign face to the sign frame or body and for adjusting the tension in the face at installation. In order to improve the appearance of display signs using the "PANAFLEX" sign facing material and standard mounting structure, additional relatively complicated framing has been required to support and also conceal the sign face mounting structure. Typical mounting systems utilize a number of components that must interact, creating added expense and requiring that a large inventory be maintained by the typical sign fabricator in order to respond to the special requirements of each particular sign. The large number of mounting components involved has caused modern sign fabrication to be unnecessarily labor intensive. The absolute amount of materials required to fabricate a single sign has also become excessive.
An example of the current state of the art relating to aluminium sign frame extrusions is disclosed in U.S. Pat. No. 4,3l7,302, issued to Von De Linde on Mar. 2, 1982. Von De Linde discloses a number of frame and clamp assemblies used to construct a flexible faced sign and to keep the sign face material under tension. In particular, Von De Linde utilizes a clamp assembly 37 which has since become the industry standard and which is also utilized by the present invention. The Von De Linde system utilizes a large number of stabilizing and interconnecting components, and also teaches the use of special tool 96 to assist with the final assembly of the sign.
One problem common to many such prior art flexible sign facing mounting systems is the difficulty with which such systems can be adapted or "retrofitted" to existing signs. Previously known systems require that existing signs be substantially dismantled if a flexible sign facing is to be applied. A large number of components would also need to be added to an existing sign to enable the conversion to a flexible sign face.
The goal of extrusion designers has since been to provide a simpler mounting structure for flexible sign facing, particularly for back lighted signs where the facing support structure should be relatively uncomplicated, compact, and lightweight without sacrificing structural strength and the ability to withstand high wind loads. The present extrusions available to the sign industry do not lend themselves to sign structures which are easy to assemble initially and which are readily servicable for changing lighting or performing other maintenance operations.